Visitor and Traversal Utilities — SQLAlchemy 2.0.0b1 documentation

Visitor and Traversal Utilities

The sqlalchemy.sql.visitors module consists of classes and functions that serve the purpose of generically traversing a Core SQL expression structure. This is not unlike the Python ast module in that is presents a system by which a program can operate upon each component of a SQL expression. Common purposes this serves are locating various kinds of elements such as _schema.Table or BindParameter objects, as well as altering the state of the structure such as replacing certain FROM clauses with others.

Note

the sqlalchemy.sql.visitors module is an internal API and is not fully public. It is subject to change and may additionally not function as expected for use patterns that aren’t considered within SQLAlchemy’s own internals.

The sqlalchemy.sql.visitors module is part of the internals of SQLAlchemy and it is not usually used by calling application code. It is however used in certain edge cases such as when constructing caching routines as well as when building out custom SQL expressions using the Custom SQL Constructs and Compilation Extension.